Gas turbine engines are defined as axial flow, rotary machines which utilize an annular combustion chamber. Gas turbines are used for a number of purposes, including powering aircraft, electric generators and pumps for oil and gas lines. Typically, a plurality of nozzles are disposed in the combustion chambers of gas turbines for spraying fuel into a stream of air passing through the chambers. The fuel is ignited and burned with oxygen to add energy to the stream of air.
The fuel system of a gas turbine includes a source of pressurized fuel, an array of fuel injection nozzles and a fuel control valve. The fuel control valve responds to power settings of the engine and adjusts the flow rate of fuel through an array of ports to the nozzles accordingly. The ports in the fuel control valve extend through the casing of the valve and are controlled by a valve element which progressively either uncovers or covers the ports to increase and decrease the flow of fuel to the engine. Each port in the valve has the same flow area for a given location of the piston so as to distribute fuel in equal amounts to the fuel nozzles in the combustion chamber. This provides uniform combustion within the combustion chamber and avoids the occurrence localized high temperature regions in the chamber.
Maintaining equality of flow distribution among a multitude of turbine injection nozzles is a constant concern, as is the need to eliminate valve-generated contamination of fuel or other injection liquids (such as water). Since low lubricity injection systems are more likely to encounter problems in flow distribution, equality of flow among of the injection nozzles of such systems is a serious concern.